HCM is a form of heart disease. A normal cat's heart is about the size of a golf ball, when HCM kicks in, it is twice that size. HCM stands for Hypertrophic (heart) Cardiomyopathy (disease). There is many types of HCM, it is very complicated. Nico had Thromboembolism Hypertrophic Cardiomyopathy (THC), that is when a cat throws a blood clot, often getting lodged in one of their major vaines in their hind legs, paralyze in the hind legs happens, unfortunately this is the worst case of HCM. When THC happened in Nico his eyes were black, his paw pads purple, his skin cold, his fur dull, and he vomited 5+ blood clots onto my bed, earlier the day he was euthanized. If your Ragdoll has THC, I beg that you put it down, because trust me -- Nothing should go through what Nico went through.
Nico dying. And yeah he peed on my bed, but who cares? He "died" when I got out of the shower that morning. I brought him back to life, but that only lasted 15 minutes until we got to the vet, then he "died" again, but they brought him back. If cats do have 9 lifes, I could see Nico's flying by one by one.
Compare this. Please beware of this, because I lost this.
Note: his black eyes.